Welding gun

ABSTRACT

A welding gun, including a contact tip assembly, a diffuser cap, a tip holder, and a shielding gas diffuser, where the shielding gas diffuser includes a casing and an axial tube extending within the casing, and where the casing and the tip holder are connected via a connection system that includes threads with reduced peaks

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional claiming priority to U.S. Ser. No.11/623,521 filed Jan. 16, 2007 which is based upon and claims thebenefit of priority from United States Provisional Application60/759,057 filed on Jan. 17, 2006 in the United States Patent andTrademark Office, the disclosures of which are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Devices, systems, and methods consistent with the invention relate to ashielding gas diffuser, and a welding gun.

2. Description of the Related Art

A welding gun is utilized to perform electric arc welding. In therelated art, a welding gun includes a welding torch at its front end,and an elongated flexible conduit at its rear end. An elongated flexibleconduit directs welding wire and shielding gas from a wire feeder to thewelding torch. The welding torch includes a contact tip, a diffuser, anozzle, and a gooseneck.

In use, the welding wire is directed through the gooseneck, diffuser,and contact tip to be welded on a work-piece. Shielding gas is directedthrough the gooseneck and is immediately diffused by orifices in thediffuser into a chamber defined by the nozzle around the contact tip, sothat the shielding gas forms a protective layer between the molten metalof the welding operation and the surrounding atmosphere.

However, this arrangement is deficient in several respects. First,during welding operations, spatter is created, especially during shortcircuit conditions. This spatter can cause substantial deterioration ofthe contact tip and diffuser over time. Second, tremendous arctemperatures are created during welding operations, and are thermallytransferred through the arc tip into the diffuser and gooseneck. Thesehigh temperatures also can cause substantial deterioration and/ordeformation of the tip, diffuser, and gooseneck, and can even cause thetip to fuse to the diffuser in some cases. Such fusing destroys thediffuser, which is a relatively expensive component of the welding gun.

The above problems demand an improvement in the related art system.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, there is provided a welding gun thatovercomes the problems of the related art.

In another aspect of the invention, there is provided a shielding gasdiffuser, including a casing and an axial tube extending within thecasing.

In another aspect of the invention, there is provided a shielding gasdiffuser, including a casing and axial tubes extending within thecasing.

In another aspect of the invention, there is provided a shielding gasdiffuser, including a casing and a connection system for a tip holder ona radially inner surface of the casing.

In another aspect of the invention, there is provided a shielding gasdiffuser, including a casing and a means for transporting shielding gasaxially within the casing.

In another aspect of the invention, there is provided a shielding gasdiffuser, including a casing and a means for connecting a tip holder ona radially inner surface of the casing.

In another aspect of the invention, there is provided a welding gunincluding a shielding gas diffuser, the shielding gas diffuser includinga casing and an axial tube extending within the casing.

In another aspect of the invention, there is provided a welding gunincluding a shielding gas diffuser, the shielding gas diffuser includinga casing and a connection system for a tip holder on a radially innersurface of the casing.

The above stated aspects, as well as other aspects, features andadvantages of the invention will become clear to those skilled in theart upon review of the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the invention will be more apparent bydescribing in detail exemplary embodiments of the invention withreference to the accompanying drawings, in which:

FIG. 1 illustrates an exploded view of a welding gun according to anexemplary embodiment of the invention;

FIG. 2 illustrates an isometric view of a handle clamp of the exemplaryembodiment of the welding gun of the invention;

FIG. 3 illustrates front, side, top and bottom views of the handle clampof the exemplary embodiment of the welding gun of the invention;

FIG. 4 illustrates front, side, rear, and sectional views of a cableconnector block of the exemplary embodiment of the welding gun of theinvention;

FIG. 5 illustrates an isometric view of a power cable male cone of theexemplary embodiment of the welding gun of the invention;

FIG. 6 illustrates front, top, and sectional views of the power cablemale cone of the exemplary embodiment of the welding gun of theinvention;

FIG. 7 illustrates an isometric view of a power cable female nut of theexemplary embodiment of the welding gun of the invention;

FIG. 8 illustrates front, side, and sectional views of the power cablefemale nut of the exemplary embodiment of the welding gun of theinvention;

FIG. 9 illustrates an isometric view of a left side handle of theexemplary embodiment of the welding gun of the invention;

FIG. 10 illustrates front, side, top, bottom, and sectional views of theleft side handle of the exemplary embodiment of the welding gun of theinvention;

FIG. 11 illustrates an isometric view of a right side handle of theexemplary embodiment of the welding gun of the invention;

FIG. 12 illustrates front, side, top, bottom, and sectional views of theright side handle of the exemplary embodiment of the welding gun of theinvention;

FIG. 13 illustrates an isometric view of a handle cap of the exemplaryembodiment of the welding gun of the invention;

FIG. 14 illustrates top, side, and sectional views of the handle cap ofthe exemplary embodiment of the welding gun of the invention;

FIG. 15 illustrates an isometric view of a handle end cap of theexemplary embodiment of the welding gun of the invention;

FIG. 16 illustrates front, top, and sectional views of the handle endcap of the exemplary embodiment of the welding gun of the invention;

FIG. 17 illustrates an isometric view of a gooseneck assembly of theexemplary embodiment of the welding gun of the invention;

FIG. 18 illustrates front, rear, side, top and bottom views of thegooseneck of the exemplary embodiment of the welding gun of theinvention;

FIG. 19 illustrates an isometric view of a diffuser of the exemplaryembodiment of the welding gun of the invention;

FIG. 20 illustrates front, rear, and side views of the diffuser of theexemplary embodiment of the welding gun of the invention;

FIG. 21 illustrates an isometric view of a tip holder of the exemplaryembodiment of the welding gun of the invention;

FIG. 22 illustrates front, top, and sectional views of the tip holder ofthe exemplary embodiment of the welding gun of the invention;

FIG. 23 illustrates the inventive thread shape of the exemplaryembodiment of the welding gun of the invention;

FIG. 24 illustrates an isometric view of a diffuser cap of the exemplaryembodiment of the welding gun of the invention;

FIG. 25 illustrates front, top, and sectional views of the diffuser capof the exemplary embodiment of the welding gun of the invention;

FIG. 26 illustrates an isometric view of a contact tip assembly of theexemplary embodiment of the welding gun of the invention;

FIG. 27 illustrates front, rear and top views of the contact tipassembly of the exemplary embodiment of the welding gun of theinvention;

FIG. 28 illustrates an isometric view of a nozzle of the exemplaryembodiment of the welding gun of the invention;

FIG. 29 illustrates front, rear, side, and top views of the nozzle ofthe exemplary embodiment of the welding gun of the invention;

FIG. 30 illustrates an isometric view of an upper gooseneck clamp of theexemplary embodiment of the welding gun of the invention;

FIG. 31 illustrates front, side, and top views of the upper gooseneckclamp of the exemplary embodiment of the welding gun of the invention;

FIG. 32 illustrates an isometric view of a lower gooseneck clamp of theexemplary embodiment of the welding gun of the invention;

FIG. 33 illustrates front, side, and top views of the lower gooseneckclamp of the exemplary embodiment of the welding gun of the invention;

FIG. 34 illustrates front, side, rear and sectional views of a rearcable connector block of the exemplary embodiment of the welding gun ofthe invention;

FIG. 35 illustrates an isometric view of a gun connector of theexemplary embodiment of the welding gun of the invention;

FIG. 36 illustrates top and sectional views of the gun connector of theexemplary embodiment of the welding gun of the invention;

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the invention will now be described below byreference to the attached Figures. The described exemplary embodimentsare intended to assist the understanding of the invention, and are notintended to limit the scope of the invention in any way. Like referencenumerals refer to like elements throughout.

An exemplary embodiment of the invention is shown in FIG. 1. In thisexemplary embodiment, welding gun 100 is an air-cooled, tandem (i.e.,having two contact tips), welding gun. But, the invention describedherein is broadly applicable to many other types of welding guns, suchas water-cooled welding guns, and welding guns with any number ofcontact tips, including only a single contact tip.

In the exemplary embodiment of FIG. 1, welding gun 100 includes nozzle110, contact tip assembly 120 (120 a), diffuser cap 130 (130 a), whichis also known as a “spatter guard,” tip holder 140 (140 a), diffuser 150(150 a), gooseneck 160 (160 a), handle clamp 170, cable connector block174 (174 a), gooseneck clamp 178, rod 180, power cable male cone 190(190 a), power cable female nut 200 (200 a), handle 210 (210 a), handlecap 220 (220 a), handle end cap 230 (230 a) and conduit 240 (240 a).

Handle clamp 170 provides a central structure for the welding gun.Handle clamp 170 is shown in more detail in FIGS. 2 and 3. Successivelyextending rearward from handle clamp 170 are cable connector block 174(FIG. 4), power cable male cone 190 (FIGS. 5 and 6), power cable femalenut 200 (FIGS. 7 and 8), and conduit 240. These features togetherprovide a continuous path for welding wire and shielding gas to besupplied from the power source to the welding gun.

Cable connector block 174, power cable male cone 190, and power cablefemale nut 200 are each enclosed within handle 210 (made up of handlehalves 211 a and 211 b), handle cap 220, and handle end cap 230 (FIGS.9-16). Handle cap 220 is provided for instances when the welding gunneeds to communicate with the welding control. Handle end cap 230 isarranged over the two handle halves (211 a and 211 b) to hold the handlehalves together.

The distal end 212 of handle 210 is restrained axially within handleclamp 170 by clamping action provided by fasteners 172. In thisexemplary embodiment, distal end 212 of handle 210 is formed in ahexagonal shape, which matches the hexagonal receiving surface 171 inhandle clamp 170. These matching shapes facilitate the clampingconnection between handle clamp 170 and handle 210, and also prevent therelative rotation of these features. Other shapes that provide thesefunctions may also be used.

Alternatively, the features extending rearward from handle clamp 170 maybe arranged in any configuration that provides the functionalitydescribed above.

Cable connector block 174 a, power cable male cone 190 a, power cablefemale nut 200 a, conduit 240 a, handle 210 a, handle cap 220 a andhandle end cap 230 a are similarly arranged.

Successively extending forward from handle clamp 170 are gooseneck 160,diffuser 150, tip holder 140, diffuser cap 130, contact tip assembly120, and nozzle 110. These features together provide a continuous pathfor welding wire and shielding gas to be supplied from the cableconnector block 174 to contact tip assembly 120.

Gooseneck 160 (FIGS. 17 and 18) is a conduit for welding wire andshielding gas to be transported to diffuser 150. The rear end 162 ofgooseneck 160 is inserted into receiving surface 176 of cable connectorblock 174 through opening 212 in handle 210. In this exemplaryembodiment, the rear end 162 is formed of a hexagonal shape, whichmatches the hexagonal shape of receiving surface 176 in cable connectorblock 174. These matching shapes facilitate the connection betweengooseneck 160 and cable connector block 174, facilitate the electricalcontact therebetween, and prevent the relative rotation of thesefeatures. Other shapes which provide this functionality may also beused. Small fasteners 179 may also be threaded into handle clamp 170and/or cable connector block 174 to axially restrain gooseneck 160.

Diffuser 150 (FIGS. 19 and 20) is arranged on distal end 164 ofgooseneck 160. In this exemplary embodiment, diffuser 150 is threaded ondistal end 164. Diffuser 150 includes axial tubes 152 within its casing151. These axial tubes travel from a groove 154 formed in the casing 151to the distal end 158 of diffuser 150. In this embodiment, groove 154 isformed distally adjacent to the distal end 164 of gooseneck 160 whendiffuser 150 is arranged thereon. Near the distal end 158 of diffuser150 are also provided radial holes 156 that connect axial tubes 152 withthe outer surface 159 of diffuser 150.

Axial tubes 152 are provided to transport shielding gas collected bygroove 154 axially within the casing 151 of diffuser 150 beforeredirecting it out of diffuser 150 through radial holes 156. This axialtransport of shielding gas helps to cool the diffuser 150—along with tipholder 140, diffuser cap 130, and contact tip assembly 120—though theprinciple of heat transfer due to the relative coolness and movement ofthe shielding gas. This provides cooling effects to diffuser 150, tipholder 140, diffuser cap 130, and contact tip assembly 120, whichprolongs their useful lives.

While groove 154 is provided in this embodiment, any groove or bafflefeature that redirects shielding gas into axial tubes 152 may beutilized.

Tip holder 140 (FIGS. 21 and 22) is arranged at the distal end 158 ofdiffuser 150. Tip holder 140 includes collar 144 which closes the distalends of the axial tubes 152 of diffuser 150, and proximal end 143, whichdeflects shielding gas into groove 154 of diffuser 150. In thisexemplary embodiment, tip holder 140 includes a long threaded rearportion 142 that is threaded into receiving threads 157 of diffuser 150.Tip holder 140 acts as an interface between diffuser 150 and contact tipassembly 120. Due to the presence of tip holder 140 between diffuser 150and contact tip assembly 120, the chances of contact tip assembly 120becoming fused to diffuser 150 due to high heat conditions iseliminated. Additionally, the long threaded rear portion 142 greatlyfacilitates heat transfer between the contact tip assembly 120, diffusercap 130, tip holder 140, and diffuser 150, and the release of that heatthrough the shielding gas flow.

Additionally, the threads on long threaded rear portion 142, and/orreceiving threads 157, may also utilize a special thread design toprovide even more improved heat transfer. This design is shown in moredetail in FIG. 23. Specifically, this special thread design incorporatesthreads that have their peaks 157 a, or high points, removed orflattened (such as by machining) The valleys 157 b may also be flattenedto correspond to opposing peaks. In traditional designs, thread peaksare subject to heat up first, and thus can become fused to mating partsin high heat conditions. The removal of these peaks prevents thisfusing. While flattened peaks are shown in this example, other shapesthat reduce the high points of the threads may also be used.

Diffuser cap 130 (FIGS. 24 and 25) is provided at the distal end of tipholder 140, and extends over collar 144 of tip holder 140, and thedistal end surface 159 of diffuser 150. Radial holes 132 are provided atthe proximal end of diffuser cap 130, and are arranged above radialholes 156 of diffuser 150. Diffuser cap 120 may be retained simply bybeing sandwiched between tip holder 140 and contact tip assembly 120, ormay have its own attachment scheme. Although it is not necessary forradial holes 132 and 156 to align, they may be designed to do so, anddiffuser cap 120 may also have an anti-rotation feature which maintainssuch an alignment. Diffuser cap 120 is a sacrificial part that protectsdiffuser 150 from spatter.

Contact tip assembly 120 (FIGS. 26 and 27) is provided at the distal endof tip holder 140 and diffuser cap 130. In this embodiment, contact tipassembly 120 has a long threaded portion 122 that threads into tipreceiving threads 148 of tip holder 140. Long threaded portion 122 is ofsufficient length to extend far into both the tip holder 140 anddiffuser 150, thereby facilitating heat transfer from contact tipassembly through tip holder 140 and diffuser 150 to the shielding gasflowing through axial tubes 152 and out through the diffusing shieldinggas. The long threaded portion 122 may extend by any length into the tipholder 140, and may have a length coextensive therewith.

The threads on the long threaded portion 122 of contact tip 120, and/orthe receiving threads 148 of tip holder 141, may also utilize thespecial thread feature discussed above (i.e., the threads may have theirpeaks removed).

Nozzle 110 (FIGS. 28 and 29) surrounds gooseneck 160, diffuser 150, tipholder 140, diffuser cap 130, contact tip assembly 120, and directs theshielding gas diffused from radial holes 156 of diffuser 150 aboutcontact tip 120 to form a protective layer between the molten metal ofthe welding operation and the surrounding atmosphere.

Gooseneck 160 a, diffuser 150 a, tip holder 140 a, diffuser cap 130 a,contact tip assembly 120 a, and nozzle 110 a are similarly arranged.

Gooseneck clamp 176 (FIGS. 30-33) supports and aligns goosenecks 160 and160 a to each other, and is made of an upper gooseneck clamp 176 a and alower gooseneck clamp 176 b, which are mated together via fasteners.

Rod 180 provides a positive adjustable stop to ensure the nozzle isadjusted to the proper axial location.

The welding gun 100 may be connected to a welding power source by a rearcable connector and gun connector, such as shown in FIGS. 34-36.

The welding gun described in the above exemplary embodiment can beemployed for hand-held welding, robotic welding and hard automation.

The welding gun described in the above exemplary embodiment employs aircooling. But, the invention is equally applicable to water cooledsystems, as a water cooling means may be added to the disclosed weldinggun and used in conjunction with the heat transfer characteristicsprovided by the axial tubes 152 in diffuser 150. Such a configurationwould provide even further improved cooling for the welding gun.

The welding gun described in the above exemplary embodiment employsfasteners is some instances. These fasteners can be any of screws,bolts, clamps, snap-fasteners, lock-fits, or any other type of fastenerthat provides similar functionality.

The welding gun described in the above exemplary embodiment employsthreaded fastening between components. However, alternative methods offastening might also be used, such as slotting, clamping, snap-fitting,or any other method that provides similar functionality.

The welding gun described in the above exemplary embodiment employsanti-rotation features between components, such as the illustratedhexagonal shapes. But, any shape that prevents rotation may be used,such as a triangle, square, pentagon, etc. Alternatively, any otheranti-rotation features, such as fins and slots, may be used.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the following claims.

What is claimed is:
 1. A shielding gas diffuser, comprising: a casing;and an axial tube extending within the casing.
 2. The shielding gasdiffuser recited in claim 1, further comprising: a groove formed in aradially inner surface of the casing, and connected to a proximal end ofthe axial tube.
 3. The shielding gas diffuser recited in claim 1,wherein: the casing further comprises a distal end and a radial holeformed in a radially outer surface of the casing near the distal end,and wherein the radial hole is connected to the axial tube.
 4. Theshielding gas diffuser recited in claim 3, wherein a distal end of theaxial tube opens to the distal end of the casing.
 5. The shielding gasdiffuser recited in claim 1, further comprising: a connection system fora tip holder on a radially inner surface of the casing.
 6. The shieldinggas diffuser recited in claim 5, wherein the connection system comprisesthreads with reduced peaks.
 7. The shielding gas diffuser recited inclaim 5, wherein the connection system is axially coextensive with theaxial tubes.
 8. A shielding gas diffuser, comprising: a casing; andaxial tubes extending within the casing.
 9. The shielding gas diffuserrecited in claim 8, further comprising: a groove formed in a radiallyinner surface of the casing and connected to proximal ends of the axialtubes.
 10. The shielding gas diffuser recited in claim 8, wherein thecasing further comprises a distal end and radial holes formed in aradially outer surface of the casing near the distal end, and whereinthe radial holes are individually connected to the axial tubes.
 11. Theshielding gas diffuser recited in claim 10, wherein distal ends of theaxial tubes open to the distal end of the casing.
 12. The shielding gasdiffuser recited in claim 8, further comprising: a connection system fora tip holder on a radially inner surface of the casing.
 13. Theshielding gas diffuser recited in claim 12, wherein the connectionsystem comprises threads with reduced peaks.
 14. The shielding gasdiffuser recited in claim 12, wherein the connection system is axiallycoextensive with the axial tubes.
 15. A shielding gas diffuser,comprising: a casing; and a connection system for a tip holder on aradially inner surface of the casing.
 16. The shielding gas diffuserrecited in claim 15, wherein the connection system comprises threadswith reduced peaks.
 17. The shielding gas diffuser recited in claim 15,wherein the casing further comprises an axial tube therein to axiallytransport shielding gas, and wherein the connection system is axiallycoextensive with the axial tube.
 18. The shielding gas diffuser recitedin claim 15, wherein the casing further comprises axial tubes therein toaxially transport shielding gas, and wherein the connection system isaxially coextensive with the axial tubes.
 19. A shielding gas diffuser,comprising: a casing; and a means for transporting shielding gas axiallywithin the casing.
 20. The shielding gas diffuser recited in claim 19,further comprising: a means for redirecting shielding gas from insidethe shielding gas diffuser into the means for transporting, wherein themeans for redirection and a proximal end of the means for transportingare connected.
 21. The shielding gas diffuser recited in claim 19,further comprising: a means for expelling shielding gas in a radialdirection out of the shielding gas diffuser near a distal end of theshielding gas diffuser, wherein the means for expelling and the meansfor transporting are connected.
 22. The shielding gas diffuser recitedin claim 19, further comprising: a means for connecting a tip holder ona radially inner surface of the casing.
 23. The shielding gas diffuserrecited in claim 22, wherein the means for connecting comprises threadswith reduced peaks.
 24. The shielding gas diffuser recited in claim 22,wherein the means for connecting is axially coextensive with the meansfor transporting.
 25. A shielding gas diffuser, comprising: a casing;and a means for connecting a tip holder on a radially inner surface ofthe casing.
 26. The shielding gas diffuser recited in claim 25, whereinthe means for connecting comprises threads with reduced peaks.
 27. Theshielding gas diffuser recited in claim 25, wherein the casing furthercomprises means for transporting shielding gas axially within thecasing, and wherein the connection system is axially coextensive withthe means for transporting.
 28. A welding gun comprising: a handleassembly including a first conduit to provide a first continuous pathfor welding wire and shield gas from a source to the welding gun; acentral handle clamp having a receiving surface for connection with thehandle assembly; a second conduit extending forward from the centralhandle clamp; a diffuser engaged with the second conduit, the diffuserhaving an outer surface an inner surface defining a central passage forthe shielding gas, the diffuser further including a plurality of tubesradially disposed about the central passage and extending between theouter and inner surfaces for transporting a shielding gas from thecentral passage; a contact tip assembly disposed within the centralpassage of the diffuser so as to transfer heat from the contact tipassembly to the shielding gas in the central passageway; a tip holder toprovide an interface between the diffuser and the contact tip assembly,the tip holder including a collar engaged with the distal end of thediffuser so as to close a distal end of each of the plurality of tubessuch that shielding gas in the axial tubes is redirected out of thediffuser; and a nozzle surrounding the contact tip assembly.
 29. Thewelding gun of claim 28, wherein the contact tip assembly comprises twocontact tips.
 30. The welding gun of claim 28, wherein the inner surfaceof the diffuser includes a redirecting surface to direct shielding gasinto the plurality of tubes.
 31. The welding gun of claim 30, whereinthe redirecting surface is one of a groove and a baffle.
 32. The weldinggun of claim 28, wherein the plurality of tubes each include a portionthat extends axially and a portion that extends radially.
 33. Thewelding gun of claim 28, wherein the diffuser and the tip holder have athreaded engagement, and wherein further at least one of the diffuserand the tip holder includes threads with flattened peaks.
 34. Thewelding gun of claim 28, further comprising: a diffuser cap at and endof the tip holder for covering at least a portion of the outer surfaceof the diffuser.
 35. The welding gun of claim 28, wherein the nozzlesurrounds the diffuser so as to direct shielding gas from the pluralityof tubes about the contact tip assembly to form a protective layerbetween a molten metal of a welding operation and a surroundingatmosphere.
 36. A welding gun comprising: a shielding gas diffuser, theshielding gas diffuser comprising, a casing having an outer surface andan inner surface disposed about a central axis, at least one axial tubeextending axially within the casing, the inner surface including adirecting feature to direct shielding gas within the casing into the atleast one axial tube, and at least one radial hole formed in the outersurface of the casing, each at least one radial hole respectivelyextending to the at least one axial tube to transport the shielding gasout of the gas diffuser.
 37. A shielding gas diffuser, the shielding gasdiffuser comprising: a casing having an outer surface and an innersurface disposed about a central axis; at least one axial tube extendingaxially within the casing, the inner surface including a directingfeature to direct shielding gas within the casing into the at least oneaxial tube; and at least one radial hole formed in the outer surface ofthe casing, each at least one radial hole respectively extending to theat least one axial tube to transport the shielding gas out of the gasdiffuser.
 38. A welding gun comprising: a shielding gas diffuser, theshielding gas diffuser comprising, a casing having an outer surface andan inner surface disposed about a central axis, and at least one axialtube extending axially within the casing, the inner surface including agroove to direct shielding gas within the casing into the at least oneaxial tube, the groove connected to a proximal end of the at least oneaxial tube.
 39. A shielding gas diffuser, the shielding gas diffusercomprising: a casing having an outer surface and an inner surfacedisposed about a central axis; and at least one axial tube extendingaxially within the casing, the inner surface including a groove todirect shielding gas within the casing into the at least one axial tube,the groove connected to a proximal end of the at least one axial tube.